
<!DOCTYPE HTML>
<html lang="zh-hans" >
    <head>
        <meta charset="UTF-8">
        <meta content="text/html; charset=utf-8" http-equiv="Content-Type">
        <title>Javascript教程 - 属性描述对象 - 小白AI.易名</title>
        <meta http-equiv="X-UA-Compatible" content="IE=edge" />
        <meta name="description" content="Javascript教程"><meta name="keywords" content="小白AI.易名,xiaobaiai.net,Javascript,入门,教程,博客">
        <meta name="generator" content="GitBook 3.2.3">
        <meta name="author" content="小白AI.易名">
        
        
    
    <link rel="stylesheet" href="../../gitbook/style.css">

    
            
                
                <link rel="stylesheet" href="../../gitbook/gitbook-plugin-chapter-fold/chapter-fold.css">
                
            
                
                <link rel="stylesheet" href="../../gitbook/gitbook-plugin-back-to-top-button/plugin.css">
                
            
                
                <link rel="stylesheet" href="../../gitbook/gitbook-plugin-search-pro/search.css">
                
            
                
                <link rel="stylesheet" href="../../gitbook/gitbook-plugin-page-footer-ex/style/plugin.css">
                
            
                
                <link rel="stylesheet" href="../../gitbook/gitbook-plugin-highlight/website.css">
                
            
                
                <link rel="stylesheet" href="../../gitbook/gitbook-plugin-search/search.css">
                
            
                
                <link rel="stylesheet" href="../../gitbook/gitbook-plugin-fontsettings/website.css">
                
            
        

    

    
        
    
        
    
        
    
        
    
        
    
        
    

        
    
    
    
    <meta name="HandheldFriendly" content="true"/>
    <meta name="viewport" content="width=device-width, initial-scale=1, user-scalable=no">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black">
    <link rel="apple-touch-icon-precomposed" sizes="152x152" href="../../gitbook/images/apple-touch-icon-precomposed-152.png">
    <link rel="shortcut icon" href="../../gitbook/images/favicon.ico" type="image/x-icon">

    
    <link rel="next" href="array.html" />
    
    
    <link rel="prev" href="object.html" />
    

    
        <link rel="shortcut icon" href='../../assets/images/favicon.ico' type="image/x-icon">
    
    
        <link rel="bookmark" href='../../assets/images/favicon.ico' type="image/x-icon">
    
    
        <link rel="apple-touch-icon" href='../../assets/images/apple-touch-icon.png'>
    
    
        
        <link rel="apple-touch-icon" sizes="120x120" href="../../assets/images/apple-touch-icon-120x120.png">
        
        <link rel="apple-touch-icon" sizes="180x180" href="../../assets/images/apple-touch-icon-180x180.png">
        
    

    </head>
    <body>
        
<div class="book">
    <div class="book-summary">
        
            
<div id="book-search-input" role="search">
    <input type="text" placeholder="输入并搜索" />
</div>

            
                <nav role="navigation">
                


<ul class="summary">
    
    

    

    
        
        
    
        <li class="chapter " data-level="1.1" data-path="../../">
            
                <a href="../../">
            
                    
                    简介
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.2" data-path="../basic/">
            
                <a href="../basic/">
            
                    
                    入门篇
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.2.1" data-path="../basic/introduction.html">
            
                <a href="../basic/introduction.html">
            
                    
                    导论
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.2.2" data-path="../basic/history.html">
            
                <a href="../basic/history.html">
            
                    
                    历史
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.2.3" data-path="../basic/grammar.html">
            
                <a href="../basic/grammar.html">
            
                    
                    基本语法
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.3" data-path="../types/">
            
                <a href="../types/">
            
                    
                    数据类型
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.3.1" data-path="../types/general.html">
            
                <a href="../types/general.html">
            
                    
                    概述
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.3.2" data-path="../types/null-undefined-boolean.html">
            
                <a href="../types/null-undefined-boolean.html">
            
                    
                    null,undefined和布尔值
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.3.3" data-path="../types/number.html">
            
                <a href="../types/number.html">
            
                    
                    数值
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.3.4" data-path="../types/string.html">
            
                <a href="../types/string.html">
            
                    
                    字符串
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.3.5" data-path="../types/object.html">
            
                <a href="../types/object.html">
            
                    
                    对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.3.6" data-path="../types/function.html">
            
                <a href="../types/function.html">
            
                    
                    函数
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.3.7" data-path="../types/array.html">
            
                <a href="../types/array.html">
            
                    
                    数组
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.4" data-path="../operators/">
            
                <a href="../operators/">
            
                    
                    运算符
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.4.1" data-path="../operators/arithmetic.html">
            
                <a href="../operators/arithmetic.html">
            
                    
                    算术运算符
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.4.2" data-path="../operators/comparison.html">
            
                <a href="../operators/comparison.html">
            
                    
                    比较运算符
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.4.3" data-path="../operators/boolean.html">
            
                <a href="../operators/boolean.html">
            
                    
                    布尔运算符
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.4.4" data-path="../operators/bit.html">
            
                <a href="../operators/bit.html">
            
                    
                    二进制位运算符
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.4.5" data-path="../operators/priority.html">
            
                <a href="../operators/priority.html">
            
                    
                    其他运算符，运算顺序
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.5" data-path="../features/">
            
                <a href="../features/">
            
                    
                    语法专题
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.5.1" data-path="../features/conversion.html">
            
                <a href="../features/conversion.html">
            
                    
                    数据类型的转换
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.5.2" data-path="../features/error.html">
            
                <a href="../features/error.html">
            
                    
                    错误处理机制
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.5.3" data-path="../features/style.html">
            
                <a href="../features/style.html">
            
                    
                    编程风格
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.5.4" data-path="../features/console.html">
            
                <a href="../features/console.html">
            
                    
                    console 对象与控制台
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.6" data-path="./">
            
                <a href="./">
            
                    
                    标准库
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.6.1" data-path="object.html">
            
                <a href="object.html">
            
                    
                    Object 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter active" data-level="1.6.2" data-path="attributes.html">
            
                <a href="attributes.html">
            
                    
                    属性描述对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.3" data-path="array.html">
            
                <a href="array.html">
            
                    
                    Array 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.4" data-path="wrapper.html">
            
                <a href="wrapper.html">
            
                    
                    包装对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.5" data-path="boolean.html">
            
                <a href="boolean.html">
            
                    
                    Boolean 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.6" data-path="number.html">
            
                <a href="number.html">
            
                    
                    Number 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.7" data-path="string.html">
            
                <a href="string.html">
            
                    
                    String 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.8" data-path="math.html">
            
                <a href="math.html">
            
                    
                    Math 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.9" data-path="date.html">
            
                <a href="date.html">
            
                    
                    Date 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.10" data-path="regexp.html">
            
                <a href="regexp.html">
            
                    
                    RegExp 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.6.11" data-path="json.html">
            
                <a href="json.html">
            
                    
                    JSON 对象
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.7" data-path="../oop/">
            
                <a href="../oop/">
            
                    
                    面向对象编程
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.7.1" data-path="../oop/new.html">
            
                <a href="../oop/new.html">
            
                    
                    实例对象与 New 命令
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.2" data-path="../oop/this.html">
            
                <a href="../oop/this.html">
            
                    
                    this 关键字
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.3" data-path="../oop/prototype.html">
            
                <a href="../oop/prototype.html">
            
                    
                    对象的继承
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.4" data-path="../oop/object.html">
            
                <a href="../oop/object.html">
            
                    
                    Object 对象的相关方法
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.7.5" data-path="../oop/strict.html">
            
                <a href="../oop/strict.html">
            
                    
                    严格模式
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.8" data-path="../async/">
            
                <a href="../async/">
            
                    
                    异步操作
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.8.1" data-path="../async/general.html">
            
                <a href="../async/general.html">
            
                    
                    概述
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.8.2" data-path="../async/timer.html">
            
                <a href="../async/timer.html">
            
                    
                    定时器
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.8.3" data-path="../async/promise.html">
            
                <a href="../async/promise.html">
            
                    
                    Promise 对象
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.9" data-path="../dom/">
            
                <a href="../dom/">
            
                    
                    DOM
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.9.1" data-path="../dom/general.html">
            
                <a href="../dom/general.html">
            
                    
                    概述
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.2" data-path="../dom/node.html">
            
                <a href="../dom/node.html">
            
                    
                    Node 接口
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.3" data-path="../dom/nodelist.html">
            
                <a href="../dom/nodelist.html">
            
                    
                    NodeList 接口，HTMLCollection 接口
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.4" data-path="../dom/parentnode.html">
            
                <a href="../dom/parentnode.html">
            
                    
                    ParentNode 接口，ChildNode 接口
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.5" data-path="../dom/document.html">
            
                <a href="../dom/document.html">
            
                    
                    Document 节点
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.6" data-path="../dom/element.html">
            
                <a href="../dom/element.html">
            
                    
                    Element 节点
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.7" data-path="../dom/attributes.html">
            
                <a href="../dom/attributes.html">
            
                    
                    属性的操作
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.8" data-path="../dom/text.html">
            
                <a href="../dom/text.html">
            
                    
                    Text 节点和 DocumentFragment 节点
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.9" data-path="../dom/css.html">
            
                <a href="../dom/css.html">
            
                    
                    CSS 操作
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.9.10" data-path="../dom/mutationobserver.html">
            
                <a href="../dom/mutationobserver.html">
            
                    
                    Mutation Observer API
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.10" data-path="../events/">
            
                <a href="../events/">
            
                    
                    事件
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.10.1" data-path="../events/eventtarget.html">
            
                <a href="../events/eventtarget.html">
            
                    
                    EventTarget 接口
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.2" data-path="../events/model.html">
            
                <a href="../events/model.html">
            
                    
                    事件模型
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.3" data-path="../events/event.html">
            
                <a href="../events/event.html">
            
                    
                    Event 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.4" data-path="../events/mouse.html">
            
                <a href="../events/mouse.html">
            
                    
                    鼠标事件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.5" data-path="../events/keyboard.html">
            
                <a href="../events/keyboard.html">
            
                    
                    键盘事件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.6" data-path="../events/progress.html">
            
                <a href="../events/progress.html">
            
                    
                    进度事件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.7" data-path="../events/form.html">
            
                <a href="../events/form.html">
            
                    
                    表单事件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.8" data-path="../events/touch.html">
            
                <a href="../events/touch.html">
            
                    
                    触摸事件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.9" data-path="../events/drag.html">
            
                <a href="../events/drag.html">
            
                    
                    拖拉事件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.10" data-path="../events/common.html">
            
                <a href="../events/common.html">
            
                    
                    其他常见事件
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.10.11" data-path="../events/globaleventhandlers.html">
            
                <a href="../events/globaleventhandlers.html">
            
                    
                    GlobalEventHandlers 接口
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.11" data-path="../bom/">
            
                <a href="../bom/">
            
                    
                    浏览器模型
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.11.1" data-path="../bom/engine.html">
            
                <a href="../bom/engine.html">
            
                    
                    浏览器模型概述
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.2" data-path="../bom/window.html">
            
                <a href="../bom/window.html">
            
                    
                    window 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.3" data-path="../bom/navigator.html">
            
                <a href="../bom/navigator.html">
            
                    
                    Navigatror 对象，Screen 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.4" data-path="../bom/cookie.html">
            
                <a href="../bom/cookie.html">
            
                    
                    Cookie
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.5" data-path="../bom/xmlhttprequest.html">
            
                <a href="../bom/xmlhttprequest.html">
            
                    
                    XMLHttpRequest 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.6" data-path="../bom/same-origin.html">
            
                <a href="../bom/same-origin.html">
            
                    
                    同源限制
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.7" data-path="../bom/cors.html">
            
                <a href="../bom/cors.html">
            
                    
                    CORS 通信
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.8" data-path="../bom/storage.html">
            
                <a href="../bom/storage.html">
            
                    
                    Storage 接口
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.9" data-path="../bom/history.html">
            
                <a href="../bom/history.html">
            
                    
                    History 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.10" data-path="../bom/location.html">
            
                <a href="../bom/location.html">
            
                    
                    Location对象，URL对象，URLSearchParams 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.11" data-path="../bom/arraybuffer.html">
            
                <a href="../bom/arraybuffer.html">
            
                    
                    ArrayBuffer 对象，Blob对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.12" data-path="../bom/file.html">
            
                <a href="../bom/file.html">
            
                    
                    File 对象，FileList 对象，FileReader 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.13" data-path="../bom/form.html">
            
                <a href="../bom/form.html">
            
                    
                    表单，FormData 对象
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.14" data-path="../bom/indexeddb.html">
            
                <a href="../bom/indexeddb.html">
            
                    
                    IndexedDB API
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.11.15" data-path="../bom/webworker.html">
            
                <a href="../bom/webworker.html">
            
                    
                    web worker
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    
        <li class="chapter " data-level="1.12" data-path="../elements/">
            
                <a href="../elements/">
            
                    
                    附录:网页元素接口
            
                </a>
            

            
            <ul class="articles">
                
    
        <li class="chapter " data-level="1.12.1" data-path="../elements/a.html">
            
                <a href="../elements/a.html">
            
                    
                    a超链接
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.2" data-path="../elements/image.html">
            
                <a href="../elements/image.html">
            
                    
                    image图片
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.3" data-path="../elements/form.html">
            
                <a href="../elements/form.html">
            
                    
                    form表单
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.4" data-path="../elements/input.html">
            
                <a href="../elements/input.html">
            
                    
                    input文本框
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.5" data-path="../elements/button.html">
            
                <a href="../elements/button.html">
            
                    
                    button按钮
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.6" data-path="../elements/option.html">
            
                <a href="../elements/option.html">
            
                    
                    option选项
            
                </a>
            

            
        </li>
    
        <li class="chapter " data-level="1.12.7" data-path="../elements/video.html">
            
                <a href="../elements/video.html">
            
                    
                    video,audio音视频
            
                </a>
            

            
        </li>
    

            </ul>
            
        </li>
    

    

    <li class="divider"></li>

    <li>
        <a href="https://www.gitbook.com" target="_blank" rel="nofollow" class="gitbook-link">
            本书使用 GitBook 发布
        </a>
    </li>
</ul>


                </nav>
            
        
    </div>

    <div class="book-body">
        
            <div class="body-inner">
                
                    

<div class="book-header" role="navigation">
    

    <!-- Title -->
    <h1>
        <i class="fa fa-circle-o-notch fa-spin"></i>
        <a href="../.." >属性描述对象</a>
    </h1>
</div>




                    <div class="page-wrapper" tabindex="-1" role="main">
                        <div class="page-inner">
                            
<div id="book-search-results">
    <div class="search-noresults">
    
<div id="book-search-results">
    <div class="search-noresults">
    
                                <section class="normal markdown-section">
                                
                                <h1 id="&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;">&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;</h1>
<h2 id="&#x6982;&#x8FF0;">&#x6982;&#x8FF0;</h2>
<p>JavaScript &#x63D0;&#x4F9B;&#x4E86;&#x4E00;&#x4E2A;&#x5185;&#x90E8;&#x6570;&#x636E;&#x7ED3;&#x6784;&#xFF0C;&#x7528;&#x6765;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x63A7;&#x5236;&#x5B83;&#x7684;&#x884C;&#x4E3A;&#xFF0C;&#x6BD4;&#x5982;&#x8BE5;&#x5C5E;&#x6027;&#x662F;&#x5426;&#x53EF;&#x5199;&#x3001;&#x53EF;&#x904D;&#x5386;&#x7B49;&#x7B49;&#x3002;&#x8FD9;&#x4E2A;&#x5185;&#x90E8;&#x6570;&#x636E;&#x7ED3;&#x6784;&#x79F0;&#x4E3A;&#x201C;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x201D;&#xFF08;attributes object&#xFF09;&#x3002;&#x6BCF;&#x4E2A;&#x5C5E;&#x6027;&#x90FD;&#x6709;&#x81EA;&#x5DF1;&#x5BF9;&#x5E94;&#x7684;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#xFF0C;&#x4FDD;&#x5B58;&#x8BE5;&#x5C5E;&#x6027;&#x7684;&#x4E00;&#x4E9B;&#x5143;&#x4FE1;&#x606F;&#x3002;</p>
<p>&#x4E0B;&#x9762;&#x662F;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;&#x4E00;&#x4E2A;&#x4F8B;&#x5B50;&#x3002;</p>
<pre><code class="lang-javascript">{
  value: <span class="hljs-number">123</span>,
  writable: <span class="hljs-literal">false</span>,
  enumerable: <span class="hljs-literal">true</span>,
  configurable: <span class="hljs-literal">false</span>,
  get: <span class="hljs-literal">undefined</span>,
  set: <span class="hljs-literal">undefined</span>
}
</code></pre>
<p>&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x63D0;&#x4F9B;6&#x4E2A;&#x5143;&#x5C5E;&#x6027;&#x3002;</p>
<p>&#xFF08;1&#xFF09;<code>value</code></p>
<p><code>value</code>&#x662F;&#x8BE5;&#x5C5E;&#x6027;&#x7684;&#x5C5E;&#x6027;&#x503C;&#xFF0C;&#x9ED8;&#x8BA4;&#x4E3A;<code>undefined</code>&#x3002;</p>
<p>&#xFF08;2&#xFF09;<code>writable</code></p>
<p><code>writable</code>&#x662F;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x8868;&#x793A;&#x5C5E;&#x6027;&#x503C;&#xFF08;value&#xFF09;&#x662F;&#x5426;&#x53EF;&#x6539;&#x53D8;&#xFF08;&#x5373;&#x662F;&#x5426;&#x53EF;&#x5199;&#xFF09;&#xFF0C;&#x9ED8;&#x8BA4;&#x4E3A;<code>true</code>&#x3002;</p>
<p>&#xFF08;3&#xFF09;<code>enumerable</code></p>
<p><code>enumerable</code>&#x662F;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x8868;&#x793A;&#x8BE5;&#x5C5E;&#x6027;&#x662F;&#x5426;&#x53EF;&#x904D;&#x5386;&#xFF0C;&#x9ED8;&#x8BA4;&#x4E3A;<code>true</code>&#x3002;&#x5982;&#x679C;&#x8BBE;&#x4E3A;<code>false</code>&#xFF0C;&#x4F1A;&#x4F7F;&#x5F97;&#x67D0;&#x4E9B;&#x64CD;&#x4F5C;&#xFF08;&#x6BD4;&#x5982;<code>for...in</code>&#x5FAA;&#x73AF;&#x3001;<code>Object.keys()</code>&#xFF09;&#x8DF3;&#x8FC7;&#x8BE5;&#x5C5E;&#x6027;&#x3002;</p>
<p>&#xFF08;4&#xFF09;<code>configurable</code></p>
<p><code>configurable</code>&#x662F;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x8868;&#x793A;&#x53EF;&#x914D;&#x7F6E;&#x6027;&#xFF0C;&#x9ED8;&#x8BA4;&#x4E3A;<code>true</code>&#x3002;&#x5982;&#x679C;&#x8BBE;&#x4E3A;<code>false</code>&#xFF0C;&#x5C06;&#x963B;&#x6B62;&#x67D0;&#x4E9B;&#x64CD;&#x4F5C;&#x6539;&#x5199;&#x8BE5;&#x5C5E;&#x6027;&#xFF0C;&#x6BD4;&#x5982;&#x65E0;&#x6CD5;&#x5220;&#x9664;&#x8BE5;&#x5C5E;&#x6027;&#xFF0C;&#x4E5F;&#x4E0D;&#x5F97;&#x6539;&#x53D8;&#x8BE5;&#x5C5E;&#x6027;&#x7684;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#xFF08;<code>value</code>&#x5C5E;&#x6027;&#x9664;&#x5916;&#xFF09;&#x3002;&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#xFF0C;<code>configurable</code>&#x5C5E;&#x6027;&#x63A7;&#x5236;&#x4E86;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;&#x53EF;&#x5199;&#x6027;&#x3002;</p>
<p>&#xFF08;5&#xFF09;<code>get</code></p>
<p><code>get</code>&#x662F;&#x4E00;&#x4E2A;&#x51FD;&#x6570;&#xFF0C;&#x8868;&#x793A;&#x8BE5;&#x5C5E;&#x6027;&#x7684;&#x53D6;&#x503C;&#x51FD;&#x6570;&#xFF08;getter&#xFF09;&#xFF0C;&#x9ED8;&#x8BA4;&#x4E3A;<code>undefined</code>&#x3002;</p>
<p>&#xFF08;6&#xFF09;<code>set</code></p>
<p><code>set</code>&#x662F;&#x4E00;&#x4E2A;&#x51FD;&#x6570;&#xFF0C;&#x8868;&#x793A;&#x8BE5;&#x5C5E;&#x6027;&#x7684;&#x5B58;&#x503C;&#x51FD;&#x6570;&#xFF08;setter&#xFF09;&#xFF0C;&#x9ED8;&#x8BA4;&#x4E3A;<code>undefined</code>&#x3002;</p>
<h2 id="objectgetownpropertydescriptor">Object.getOwnPropertyDescriptor()</h2>
<p><code>Object.getOwnPropertyDescriptor()</code>&#x65B9;&#x6CD5;&#x53EF;&#x4EE5;&#x83B7;&#x53D6;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x3002;&#x5B83;&#x7684;&#x7B2C;&#x4E00;&#x4E2A;&#x53C2;&#x6570;&#x662F;&#x76EE;&#x6807;&#x5BF9;&#x8C61;&#xFF0C;&#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;&#x662F;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x5BF9;&#x5E94;&#x76EE;&#x6807;&#x5BF9;&#x8C61;&#x7684;&#x67D0;&#x4E2A;&#x5C5E;&#x6027;&#x540D;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = { p: <span class="hljs-string">&apos;a&apos;</span> };

<span class="hljs-built_in">Object</span>.getOwnPropertyDescriptor(obj, <span class="hljs-string">&apos;p&apos;</span>)
<span class="hljs-comment">// Object { value: &quot;a&quot;,</span>
<span class="hljs-comment">//   writable: true,</span>
<span class="hljs-comment">//   enumerable: true,</span>
<span class="hljs-comment">//   configurable: true</span>
<span class="hljs-comment">// }</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>Object.getOwnPropertyDescriptor()</code>&#x65B9;&#x6CD5;&#x83B7;&#x53D6;<code>obj.p</code>&#x7684;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;<code>Object.getOwnPropertyDescriptor()</code>&#x65B9;&#x6CD5;&#x53EA;&#x80FD;&#x7528;&#x4E8E;&#x5BF9;&#x8C61;&#x81EA;&#x8EAB;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x4E0D;&#x80FD;&#x7528;&#x4E8E;&#x7EE7;&#x627F;&#x7684;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = { p: <span class="hljs-string">&apos;a&apos;</span> };

<span class="hljs-built_in">Object</span>.getOwnPropertyDescriptor(obj, <span class="hljs-string">&apos;toString&apos;</span>)
<span class="hljs-comment">// undefined</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>toString</code>&#x662F;<code>obj</code>&#x5BF9;&#x8C61;&#x7EE7;&#x627F;&#x7684;&#x5C5E;&#x6027;&#xFF0C;<code>Object.getOwnPropertyDescriptor()</code>&#x65E0;&#x6CD5;&#x83B7;&#x53D6;&#x3002;</p>
<h2 id="objectgetownpropertynames">Object.getOwnPropertyNames()</h2>
<p><code>Object.getOwnPropertyNames</code>&#x65B9;&#x6CD5;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x6570;&#x7EC4;&#xFF0C;&#x6210;&#x5458;&#x662F;&#x53C2;&#x6570;&#x5BF9;&#x8C61;&#x81EA;&#x8EAB;&#x7684;&#x5168;&#x90E8;&#x5C5E;&#x6027;&#x7684;&#x5C5E;&#x6027;&#x540D;&#xFF0C;&#x4E0D;&#x7BA1;&#x8BE5;&#x5C5E;&#x6027;&#x662F;&#x5426;&#x53EF;&#x904D;&#x5386;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperties({}, {
  p1: { value: <span class="hljs-number">1</span>, enumerable: <span class="hljs-literal">true</span> },
  p2: { value: <span class="hljs-number">2</span>, enumerable: <span class="hljs-literal">false</span> }
});

<span class="hljs-built_in">Object</span>.getOwnPropertyNames(obj)
<span class="hljs-comment">// [&quot;p1&quot;, &quot;p2&quot;]</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.p1</code>&#x662F;&#x53EF;&#x904D;&#x5386;&#x7684;&#xFF0C;<code>obj.p2</code>&#x662F;&#x4E0D;&#x53EF;&#x904D;&#x5386;&#x7684;&#x3002;<code>Object.getOwnPropertyNames</code>&#x4F1A;&#x5C06;&#x5B83;&#x4EEC;&#x90FD;&#x8FD4;&#x56DE;&#x3002;</p>
<p>&#x8FD9;&#x8DDF;<code>Object.keys</code>&#x7684;&#x884C;&#x4E3A;&#x4E0D;&#x540C;&#xFF0C;<code>Object.keys</code>&#x53EA;&#x8FD4;&#x56DE;&#x5BF9;&#x8C61;&#x81EA;&#x8EAB;&#x7684;&#x53EF;&#x904D;&#x5386;&#x5C5E;&#x6027;&#x7684;&#x5168;&#x90E8;&#x5C5E;&#x6027;&#x540D;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-built_in">Object</span>.keys([]) <span class="hljs-comment">// []</span>
<span class="hljs-built_in">Object</span>.getOwnPropertyNames([]) <span class="hljs-comment">// [ &apos;length&apos; ]</span>

<span class="hljs-built_in">Object</span>.keys(<span class="hljs-built_in">Object</span>.prototype) <span class="hljs-comment">// []</span>
<span class="hljs-built_in">Object</span>.getOwnPropertyNames(<span class="hljs-built_in">Object</span>.prototype)
<span class="hljs-comment">// [&apos;hasOwnProperty&apos;,</span>
<span class="hljs-comment">//  &apos;valueOf&apos;,</span>
<span class="hljs-comment">//  &apos;constructor&apos;,</span>
<span class="hljs-comment">//  &apos;toLocaleString&apos;,</span>
<span class="hljs-comment">//  &apos;isPrototypeOf&apos;,</span>
<span class="hljs-comment">//  &apos;propertyIsEnumerable&apos;,</span>
<span class="hljs-comment">//  &apos;toString&apos;]</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x6570;&#x7EC4;&#x81EA;&#x8EAB;&#x7684;<code>length</code>&#x5C5E;&#x6027;&#x662F;&#x4E0D;&#x53EF;&#x904D;&#x5386;&#x7684;&#xFF0C;<code>Object.keys</code>&#x4E0D;&#x4F1A;&#x8FD4;&#x56DE;&#x8BE5;&#x5C5E;&#x6027;&#x3002;&#x7B2C;&#x4E8C;&#x4E2A;&#x4F8B;&#x5B50;&#x7684;<code>Object.prototype</code>&#x4E5F;&#x662F;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x6240;&#x6709;&#x5B9E;&#x4F8B;&#x5BF9;&#x8C61;&#x90FD;&#x4F1A;&#x7EE7;&#x627F;&#x5B83;&#xFF0C;&#x5B83;&#x81EA;&#x8EAB;&#x7684;&#x5C5E;&#x6027;&#x90FD;&#x662F;&#x4E0D;&#x53EF;&#x904D;&#x5386;&#x7684;&#x3002;</p>
<h2 id="objectdefineproperty&#xFF0C;objectdefineproperties">Object.defineProperty()&#xFF0C;Object.defineProperties()</h2>
<p><code>Object.defineProperty()</code>&#x65B9;&#x6CD5;&#x5141;&#x8BB8;&#x901A;&#x8FC7;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#xFF0C;&#x5B9A;&#x4E49;&#x6216;&#x4FEE;&#x6539;&#x4E00;&#x4E2A;&#x5C5E;&#x6027;&#xFF0C;&#x7136;&#x540E;&#x8FD4;&#x56DE;&#x4FEE;&#x6539;&#x540E;&#x7684;&#x5BF9;&#x8C61;&#xFF0C;&#x5B83;&#x7684;&#x7528;&#x6CD5;&#x5982;&#x4E0B;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-built_in">Object</span>.defineProperty(object, propertyName, attributesObject)
</code></pre>
<p><code>Object.defineProperty</code>&#x65B9;&#x6CD5;&#x63A5;&#x53D7;&#x4E09;&#x4E2A;&#x53C2;&#x6570;&#xFF0C;&#x4F9D;&#x6B21;&#x5982;&#x4E0B;&#x3002;</p>
<ul>
<li>object&#xFF1A;&#x5C5E;&#x6027;&#x6240;&#x5728;&#x7684;&#x5BF9;&#x8C61;</li>
<li>propertyName&#xFF1A;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x8868;&#x793A;&#x5C5E;&#x6027;&#x540D;</li>
<li>attributesObject&#xFF1A;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;</li>
</ul>
<p>&#x4E3E;&#x4F8B;&#x6765;&#x8BF4;&#xFF0C;&#x5B9A;&#x4E49;<code>obj.p</code>&#x53EF;&#x4EE5;&#x5199;&#x6210;&#x4E0B;&#x9762;&#x8FD9;&#x6837;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-number">123</span>,
  writable: <span class="hljs-literal">false</span>,
  enumerable: <span class="hljs-literal">true</span>,
  configurable: <span class="hljs-literal">false</span>
});

obj.p <span class="hljs-comment">// 123</span>

obj.p = <span class="hljs-number">246</span>;
obj.p <span class="hljs-comment">// 123</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>Object.defineProperty()</code>&#x65B9;&#x6CD5;&#x5B9A;&#x4E49;&#x4E86;<code>obj.p</code>&#x5C5E;&#x6027;&#x3002;&#x7531;&#x4E8E;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;<code>writable</code>&#x5C5E;&#x6027;&#x4E3A;<code>false</code>&#xFF0C;&#x6240;&#x4EE5;<code>obj.p</code>&#x5C5E;&#x6027;&#x4E0D;&#x53EF;&#x5199;&#x3002;&#x6CE8;&#x610F;&#xFF0C;&#x8FD9;&#x91CC;&#x7684;<code>Object.defineProperty</code>&#x65B9;&#x6CD5;&#x7684;&#x7B2C;&#x4E00;&#x4E2A;&#x53C2;&#x6570;&#x662F;<code>{}</code>&#xFF08;&#x4E00;&#x4E2A;&#x65B0;&#x5EFA;&#x7684;&#x7A7A;&#x5BF9;&#x8C61;&#xFF09;&#xFF0C;<code>p</code>&#x5C5E;&#x6027;&#x76F4;&#x63A5;&#x5B9A;&#x4E49;&#x5728;&#x8FD9;&#x4E2A;&#x7A7A;&#x5BF9;&#x8C61;&#x4E0A;&#x9762;&#xFF0C;&#x7136;&#x540E;&#x8FD4;&#x56DE;&#x8FD9;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x8FD9;&#x662F;<code>Object.defineProperty()</code>&#x7684;&#x5E38;&#x89C1;&#x7528;&#x6CD5;&#x3002;</p>
<p>&#x5982;&#x679C;&#x5C5E;&#x6027;&#x5DF2;&#x7ECF;&#x5B58;&#x5728;&#xFF0C;<code>Object.defineProperty()</code>&#x65B9;&#x6CD5;&#x76F8;&#x5F53;&#x4E8E;&#x66F4;&#x65B0;&#x8BE5;&#x5C5E;&#x6027;&#x7684;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x3002;</p>
<p>&#x5982;&#x679C;&#x4E00;&#x6B21;&#x6027;&#x5B9A;&#x4E49;&#x6216;&#x4FEE;&#x6539;&#x591A;&#x4E2A;&#x5C5E;&#x6027;&#xFF0C;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;<code>Object.defineProperties()</code>&#x65B9;&#x6CD5;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperties({}, {
  p1: { value: <span class="hljs-number">123</span>, enumerable: <span class="hljs-literal">true</span> },
  p2: { value: <span class="hljs-string">&apos;abc&apos;</span>, enumerable: <span class="hljs-literal">true</span> },
  p3: { get: <span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) </span>{ <span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.p1 + <span class="hljs-keyword">this</span>.p2 },
    enumerable:<span class="hljs-literal">true</span>,
    configurable:<span class="hljs-literal">true</span>
  }
});

obj.p1 <span class="hljs-comment">// 123</span>
obj.p2 <span class="hljs-comment">// &quot;abc&quot;</span>
obj.p3 <span class="hljs-comment">// &quot;123abc&quot;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>Object.defineProperties()</code>&#x540C;&#x65F6;&#x5B9A;&#x4E49;&#x4E86;<code>obj</code>&#x5BF9;&#x8C61;&#x7684;&#x4E09;&#x4E2A;&#x5C5E;&#x6027;&#x3002;&#x5176;&#x4E2D;&#xFF0C;<code>p3</code>&#x5C5E;&#x6027;&#x5B9A;&#x4E49;&#x4E86;&#x53D6;&#x503C;&#x51FD;&#x6570;<code>get</code>&#xFF0C;&#x5373;&#x6BCF;&#x6B21;&#x8BFB;&#x53D6;&#x8BE5;&#x5C5E;&#x6027;&#xFF0C;&#x90FD;&#x4F1A;&#x8C03;&#x7528;&#x8FD9;&#x4E2A;&#x53D6;&#x503C;&#x51FD;&#x6570;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;&#x4E00;&#x65E6;&#x5B9A;&#x4E49;&#x4E86;&#x53D6;&#x503C;&#x51FD;&#x6570;<code>get</code>&#xFF08;&#x6216;&#x5B58;&#x503C;&#x51FD;&#x6570;<code>set</code>&#xFF09;&#xFF0C;&#x5C31;&#x4E0D;&#x80FD;&#x5C06;<code>writable</code>&#x5C5E;&#x6027;&#x8BBE;&#x4E3A;<code>true</code>&#xFF0C;&#x6216;&#x8005;&#x540C;&#x65F6;&#x5B9A;&#x4E49;<code>value</code>&#x5C5E;&#x6027;&#xFF0C;&#x5426;&#x5219;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {};

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-number">123</span>,
  get: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{ <span class="hljs-keyword">return</span> <span class="hljs-number">456</span>; }
});
<span class="hljs-comment">// TypeError: Invalid property.</span>
<span class="hljs-comment">// A property cannot both have accessors and be writable or have a value</span>

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {
  writable: <span class="hljs-literal">true</span>,
  get: <span class="hljs-function"><span class="hljs-keyword">function</span>(<span class="hljs-params"></span>) </span>{ <span class="hljs-keyword">return</span> <span class="hljs-number">456</span>; }
});
<span class="hljs-comment">// TypeError: Invalid property descriptor.</span>
<span class="hljs-comment">// Cannot both specify accessors and a value or writable attribute</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x540C;&#x65F6;&#x5B9A;&#x4E49;&#x4E86;<code>get</code>&#x5C5E;&#x6027;&#x548C;<code>value</code>&#x5C5E;&#x6027;&#xFF0C;&#x4EE5;&#x53CA;&#x5C06;<code>writable</code>&#x5C5E;&#x6027;&#x8BBE;&#x4E3A;<code>true</code>&#xFF0C;&#x5C31;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<p><code>Object.defineProperty()</code>&#x548C;<code>Object.defineProperties()</code>&#x53C2;&#x6570;&#x91CC;&#x9762;&#x7684;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#xFF0C;<code>writable</code>&#x3001;<code>configurable</code>&#x3001;<code>enumerable</code>&#x8FD9;&#x4E09;&#x4E2A;&#x5C5E;&#x6027;&#x7684;&#x9ED8;&#x8BA4;&#x503C;&#x90FD;&#x4E3A;<code>false</code>&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {};
<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;foo&apos;</span>, {});
<span class="hljs-built_in">Object</span>.getOwnPropertyDescriptor(obj, <span class="hljs-string">&apos;foo&apos;</span>)
<span class="hljs-comment">// {</span>
<span class="hljs-comment">//   value: undefined,</span>
<span class="hljs-comment">//   writable: false,</span>
<span class="hljs-comment">//   enumerable: false,</span>
<span class="hljs-comment">//   configurable: false</span>
<span class="hljs-comment">// }</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x5B9A;&#x4E49;<code>obj.foo</code>&#x65F6;&#x7528;&#x4E86;&#x4E00;&#x4E2A;&#x7A7A;&#x7684;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#xFF0C;&#x5C31;&#x53EF;&#x4EE5;&#x770B;&#x5230;&#x5404;&#x4E2A;&#x5143;&#x5C5E;&#x6027;&#x7684;&#x9ED8;&#x8BA4;&#x503C;&#x3002;</p>
<h2 id="objectprototypepropertyisenumerable">Object.prototype.propertyIsEnumerable()</h2>
<p>&#x5B9E;&#x4F8B;&#x5BF9;&#x8C61;&#x7684;<code>propertyIsEnumerable()</code>&#x65B9;&#x6CD5;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x7528;&#x6765;&#x5224;&#x65AD;&#x67D0;&#x4E2A;&#x5C5E;&#x6027;&#x662F;&#x5426;&#x53EF;&#x904D;&#x5386;&#x3002;&#x6CE8;&#x610F;&#xFF0C;&#x8FD9;&#x4E2A;&#x65B9;&#x6CD5;&#x53EA;&#x80FD;&#x7528;&#x4E8E;&#x5224;&#x65AD;&#x5BF9;&#x8C61;&#x81EA;&#x8EAB;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x5BF9;&#x4E8E;&#x7EE7;&#x627F;&#x7684;&#x5C5E;&#x6027;&#x4E00;&#x5F8B;&#x8FD4;&#x56DE;<code>false</code>&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {};
obj.p = <span class="hljs-number">123</span>;

obj.propertyIsEnumerable(<span class="hljs-string">&apos;p&apos;</span>) <span class="hljs-comment">// true</span>
obj.propertyIsEnumerable(<span class="hljs-string">&apos;toString&apos;</span>) <span class="hljs-comment">// false</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.p</code>&#x662F;&#x53EF;&#x904D;&#x5386;&#x7684;&#xFF0C;&#x800C;<code>obj.toString</code>&#x662F;&#x7EE7;&#x627F;&#x7684;&#x5C5E;&#x6027;&#x3002;</p>
<h2 id="&#x5143;&#x5C5E;&#x6027;">&#x5143;&#x5C5E;&#x6027;</h2>
<p>&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;&#x5404;&#x4E2A;&#x5C5E;&#x6027;&#x79F0;&#x4E3A;&#x201C;&#x5143;&#x5C5E;&#x6027;&#x201D;&#xFF0C;&#x56E0;&#x4E3A;&#x5B83;&#x4EEC;&#x53EF;&#x4EE5;&#x770B;&#x4F5C;&#x662F;&#x63A7;&#x5236;&#x5C5E;&#x6027;&#x7684;&#x5C5E;&#x6027;&#x3002;</p>
<h3 id="value">value</h3>
<p><code>value</code>&#x5C5E;&#x6027;&#x662F;&#x76EE;&#x6807;&#x5C5E;&#x6027;&#x7684;&#x503C;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {};
obj.p = <span class="hljs-number">123</span>;

<span class="hljs-built_in">Object</span>.getOwnPropertyDescriptor(obj, <span class="hljs-string">&apos;p&apos;</span>).value
<span class="hljs-comment">// 123</span>

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, { value: <span class="hljs-number">246</span> });
obj.p <span class="hljs-comment">// 246</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x662F;&#x901A;&#x8FC7;<code>value</code>&#x5C5E;&#x6027;&#xFF0C;&#x8BFB;&#x53D6;&#x6216;&#x6539;&#x5199;<code>obj.p</code>&#x7684;&#x4F8B;&#x5B50;&#x3002;</p>
<h3 id="writable">writable</h3>
<p><code>writable</code>&#x5C5E;&#x6027;&#x662F;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x51B3;&#x5B9A;&#x4E86;&#x76EE;&#x6807;&#x5C5E;&#x6027;&#x7684;&#x503C;&#xFF08;value&#xFF09;&#x662F;&#x5426;&#x53EF;&#x4EE5;&#x88AB;&#x6539;&#x53D8;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {};

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;a&apos;</span>, {
  value: <span class="hljs-number">37</span>,
  writable: <span class="hljs-literal">false</span>
});

obj.a <span class="hljs-comment">// 37</span>
obj.a = <span class="hljs-number">25</span>;
obj.a <span class="hljs-comment">// 37</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.a</code>&#x7684;<code>writable</code>&#x5C5E;&#x6027;&#x662F;<code>false</code>&#x3002;&#x7136;&#x540E;&#xFF0C;&#x6539;&#x53D8;<code>obj.a</code>&#x7684;&#x503C;&#xFF0C;&#x4E0D;&#x4F1A;&#x6709;&#x4EFB;&#x4F55;&#x6548;&#x679C;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;&#x6B63;&#x5E38;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x5BF9;<code>writable</code>&#x4E3A;<code>false</code>&#x7684;&#x5C5E;&#x6027;&#x8D4B;&#x503C;&#x4E0D;&#x4F1A;&#x62A5;&#x9519;&#xFF0C;&#x53EA;&#x4F1A;&#x9ED8;&#x9ED8;&#x5931;&#x8D25;&#x3002;&#x4F46;&#x662F;&#xFF0C;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#x4F1A;&#x62A5;&#x9519;&#xFF0C;&#x5373;&#x4F7F;&#x5BF9;<code>a</code>&#x5C5E;&#x6027;&#x91CD;&#x65B0;&#x8D4B;&#x4E88;&#x4E00;&#x4E2A;&#x540C;&#x6837;&#x7684;&#x503C;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-meta">&apos;use strict&apos;</span>;
<span class="hljs-keyword">var</span> obj = {};

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;a&apos;</span>, {
  value: <span class="hljs-number">37</span>,
  writable: <span class="hljs-literal">false</span>
});

obj.a = <span class="hljs-number">37</span>;
<span class="hljs-comment">// Uncaught TypeError: Cannot assign to read only property &apos;a&apos; of object</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF0C;&#x5BF9;<code>obj.a</code>&#x4EFB;&#x4F55;&#x8D4B;&#x503C;&#x884C;&#x4E3A;&#x90FD;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<p>&#x5982;&#x679C;&#x539F;&#x578B;&#x5BF9;&#x8C61;&#x7684;&#x67D0;&#x4E2A;&#x5C5E;&#x6027;&#x7684;<code>writable</code>&#x4E3A;<code>false</code>&#xFF0C;&#x90A3;&#x4E48;&#x5B50;&#x5BF9;&#x8C61;&#x5C06;&#x65E0;&#x6CD5;&#x81EA;&#x5B9A;&#x4E49;&#x8FD9;&#x4E2A;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> proto = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;foo&apos;</span>, {
  value: <span class="hljs-string">&apos;a&apos;</span>,
  writable: <span class="hljs-literal">false</span>
});

<span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.create(proto);

obj.foo = <span class="hljs-string">&apos;b&apos;</span>;
obj.foo <span class="hljs-comment">// &apos;a&apos;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>proto</code>&#x662F;&#x539F;&#x578B;&#x5BF9;&#x8C61;&#xFF0C;&#x5B83;&#x7684;<code>foo</code>&#x5C5E;&#x6027;&#x4E0D;&#x53EF;&#x5199;&#x3002;<code>obj</code>&#x5BF9;&#x8C61;&#x7EE7;&#x627F;<code>proto</code>&#xFF0C;&#x4E5F;&#x4E0D;&#x53EF;&#x4EE5;&#x518D;&#x81EA;&#x5B9A;&#x4E49;&#x8FD9;&#x4E2A;&#x5C5E;&#x6027;&#x4E86;&#x3002;&#x5982;&#x679C;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF0C;&#x8FD9;&#x6837;&#x505A;&#x8FD8;&#x4F1A;&#x629B;&#x51FA;&#x4E00;&#x4E2A;&#x9519;&#x8BEF;&#x3002;</p>
<p>&#x4F46;&#x662F;&#xFF0C;&#x6709;&#x4E00;&#x4E2A;&#x89C4;&#x907F;&#x65B9;&#x6CD5;&#xFF0C;&#x5C31;&#x662F;&#x901A;&#x8FC7;&#x8986;&#x76D6;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#xFF0C;&#x7ED5;&#x8FC7;&#x8FD9;&#x4E2A;&#x9650;&#x5236;&#x3002;&#x539F;&#x56E0;&#x662F;&#x8FD9;&#x79CD;&#x60C5;&#x51B5;&#x4E0B;&#xFF0C;&#x539F;&#x578B;&#x94FE;&#x4F1A;&#x88AB;&#x5B8C;&#x5168;&#x5FFD;&#x89C6;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> proto = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;foo&apos;</span>, {
  value: <span class="hljs-string">&apos;a&apos;</span>,
  writable: <span class="hljs-literal">false</span>
});

<span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.create(proto);
<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;foo&apos;</span>, {
  value: <span class="hljs-string">&apos;b&apos;</span>
});

obj.foo <span class="hljs-comment">// &quot;b&quot;</span>
</code></pre>
<h3 id="enumerable">enumerable</h3>
<p><code>enumerable</code>&#xFF08;&#x53EF;&#x904D;&#x5386;&#x6027;&#xFF09;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x8868;&#x793A;&#x76EE;&#x6807;&#x5C5E;&#x6027;&#x662F;&#x5426;&#x53EF;&#x904D;&#x5386;&#x3002;</p>
<p>JavaScript &#x7684;&#x65E9;&#x671F;&#x7248;&#x672C;&#xFF0C;<code>for...in</code>&#x5FAA;&#x73AF;&#x662F;&#x57FA;&#x4E8E;<code>in</code>&#x8FD0;&#x7B97;&#x7B26;&#x7684;&#x3002;&#x6211;&#x4EEC;&#x77E5;&#x9053;&#xFF0C;<code>in</code>&#x8FD0;&#x7B97;&#x7B26;&#x4E0D;&#x7BA1;&#x67D0;&#x4E2A;&#x5C5E;&#x6027;&#x662F;&#x5BF9;&#x8C61;&#x81EA;&#x8EAB;&#x7684;&#x8FD8;&#x662F;&#x7EE7;&#x627F;&#x7684;&#xFF0C;&#x90FD;&#x4F1A;&#x8FD4;&#x56DE;<code>true</code>&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {};
<span class="hljs-string">&apos;toString&apos;</span> <span class="hljs-keyword">in</span> obj <span class="hljs-comment">// true</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>toString</code>&#x4E0D;&#x662F;<code>obj</code>&#x5BF9;&#x8C61;&#x81EA;&#x8EAB;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x4F46;&#x662F;<code>in</code>&#x8FD0;&#x7B97;&#x7B26;&#x4E5F;&#x8FD4;&#x56DE;<code>true</code>&#xFF0C;&#x8FD9;&#x5BFC;&#x81F4;&#x4E86;<code>toString</code>&#x5C5E;&#x6027;&#x4E5F;&#x4F1A;&#x88AB;<code>for...in</code>&#x5FAA;&#x73AF;&#x904D;&#x5386;&#x3002;</p>
<p>&#x8FD9;&#x663E;&#x7136;&#x4E0D;&#x592A;&#x5408;&#x7406;&#xFF0C;&#x540E;&#x6765;&#x5C31;&#x5F15;&#x5165;&#x4E86;&#x201C;&#x53EF;&#x904D;&#x5386;&#x6027;&#x201D;&#x8FD9;&#x4E2A;&#x6982;&#x5FF5;&#x3002;&#x53EA;&#x6709;&#x53EF;&#x904D;&#x5386;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x624D;&#x4F1A;&#x88AB;<code>for...in</code>&#x5FAA;&#x73AF;&#x904D;&#x5386;&#xFF0C;&#x540C;&#x65F6;&#x8FD8;&#x89C4;&#x5B9A;<code>toString</code>&#x8FD9;&#x4E00;&#x7C7B;&#x5B9E;&#x4F8B;&#x5BF9;&#x8C61;&#x7EE7;&#x627F;&#x7684;&#x539F;&#x751F;&#x5C5E;&#x6027;&#xFF0C;&#x90FD;&#x662F;&#x4E0D;&#x53EF;&#x904D;&#x5386;&#x7684;&#xFF0C;&#x8FD9;&#x6837;&#x5C31;&#x4FDD;&#x8BC1;&#x4E86;<code>for...in</code>&#x5FAA;&#x73AF;&#x7684;&#x53EF;&#x7528;&#x6027;&#x3002;</p>
<p>&#x5177;&#x4F53;&#x6765;&#x8BF4;&#xFF0C;&#x5982;&#x679C;&#x4E00;&#x4E2A;&#x5C5E;&#x6027;&#x7684;<code>enumerable</code>&#x4E3A;<code>false</code>&#xFF0C;&#x4E0B;&#x9762;&#x4E09;&#x4E2A;&#x64CD;&#x4F5C;&#x4E0D;&#x4F1A;&#x53D6;&#x5230;&#x8BE5;&#x5C5E;&#x6027;&#x3002;</p>
<ul>
<li><code>for..in</code>&#x5FAA;&#x73AF;</li>
<li><code>Object.keys</code>&#x65B9;&#x6CD5;</li>
<li><code>JSON.stringify</code>&#x65B9;&#x6CD5;</li>
</ul>
<p>&#x56E0;&#x6B64;&#xFF0C;<code>enumerable</code>&#x53EF;&#x4EE5;&#x7528;&#x6765;&#x8BBE;&#x7F6E;&#x201C;&#x79D8;&#x5BC6;&#x201D;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {};

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;x&apos;</span>, {
  value: <span class="hljs-number">123</span>,
  enumerable: <span class="hljs-literal">false</span>
});

obj.x <span class="hljs-comment">// 123</span>

<span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> key <span class="hljs-keyword">in</span> obj) {
  <span class="hljs-built_in">console</span>.log(key);
}
<span class="hljs-comment">// undefined</span>

<span class="hljs-built_in">Object</span>.keys(obj)  <span class="hljs-comment">// []</span>
<span class="hljs-built_in">JSON</span>.stringify(obj) <span class="hljs-comment">// &quot;{}&quot;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.x</code>&#x5C5E;&#x6027;&#x7684;<code>enumerable</code>&#x4E3A;<code>false</code>&#xFF0C;&#x6240;&#x4EE5;&#x4E00;&#x822C;&#x7684;&#x904D;&#x5386;&#x64CD;&#x4F5C;&#x90FD;&#x65E0;&#x6CD5;&#x83B7;&#x53D6;&#x8BE5;&#x5C5E;&#x6027;&#xFF0C;&#x4F7F;&#x5F97;&#x5B83;&#x6709;&#x70B9;&#x50CF;&#x201C;&#x79D8;&#x5BC6;&#x201D;&#x5C5E;&#x6027;&#xFF0C;&#x4F46;&#x4E0D;&#x662F;&#x771F;&#x6B63;&#x7684;&#x79C1;&#x6709;&#x5C5E;&#x6027;&#xFF0C;&#x8FD8;&#x662F;&#x53EF;&#x4EE5;&#x76F4;&#x63A5;&#x83B7;&#x53D6;&#x5B83;&#x7684;&#x503C;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;<code>for...in</code>&#x5FAA;&#x73AF;&#x5305;&#x62EC;&#x7EE7;&#x627F;&#x7684;&#x5C5E;&#x6027;&#xFF0C;<code>Object.keys</code>&#x65B9;&#x6CD5;&#x4E0D;&#x5305;&#x62EC;&#x7EE7;&#x627F;&#x7684;&#x5C5E;&#x6027;&#x3002;&#x5982;&#x679C;&#x9700;&#x8981;&#x83B7;&#x53D6;&#x5BF9;&#x8C61;&#x81EA;&#x8EAB;&#x7684;&#x6240;&#x6709;&#x5C5E;&#x6027;&#xFF0C;&#x4E0D;&#x7BA1;&#x662F;&#x5426;&#x53EF;&#x904D;&#x5386;&#xFF0C;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;<code>Object.getOwnPropertyNames</code>&#x65B9;&#x6CD5;&#x3002;</p>
<p>&#x53E6;&#x5916;&#xFF0C;<code>JSON.stringify</code>&#x65B9;&#x6CD5;&#x4F1A;&#x6392;&#x9664;<code>enumerable</code>&#x4E3A;<code>false</code>&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x6709;&#x65F6;&#x53EF;&#x4EE5;&#x5229;&#x7528;&#x8FD9;&#x4E00;&#x70B9;&#x3002;&#x5982;&#x679C;&#x5BF9;&#x8C61;&#x7684; JSON &#x683C;&#x5F0F;&#x8F93;&#x51FA;&#x8981;&#x6392;&#x9664;&#x67D0;&#x4E9B;&#x5C5E;&#x6027;&#xFF0C;&#x5C31;&#x53EF;&#x4EE5;&#x628A;&#x8FD9;&#x4E9B;&#x5C5E;&#x6027;&#x7684;<code>enumerable</code>&#x8BBE;&#x4E3A;<code>false</code>&#x3002;</p>
<h3 id="configurable">configurable</h3>
<p><code>configurable</code>(&#x53EF;&#x914D;&#x7F6E;&#x6027;&#xFF09;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x5E03;&#x5C14;&#x503C;&#xFF0C;&#x51B3;&#x5B9A;&#x4E86;&#x662F;&#x5426;&#x53EF;&#x4EE5;&#x4FEE;&#x6539;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x3002;&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#xFF0C;<code>configurable</code>&#x4E3A;<code>false</code>&#x65F6;&#xFF0C;<code>value</code>&#x3001;<code>writable</code>&#x3001;<code>enumerable</code>&#x548C;<code>configurable</code>&#x90FD;&#x4E0D;&#x80FD;&#x88AB;&#x4FEE;&#x6539;&#x4E86;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-number">1</span>,
  writable: <span class="hljs-literal">false</span>,
  enumerable: <span class="hljs-literal">false</span>,
  configurable: <span class="hljs-literal">false</span>
});

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {value: <span class="hljs-number">2</span>})
<span class="hljs-comment">// TypeError: Cannot redefine property: p</span>

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {writable: <span class="hljs-literal">true</span>})
<span class="hljs-comment">// TypeError: Cannot redefine property: p</span>

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {enumerable: <span class="hljs-literal">true</span>})
<span class="hljs-comment">// TypeError: Cannot redefine property: p</span>

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {configurable: <span class="hljs-literal">true</span>})
<span class="hljs-comment">// TypeError: Cannot redefine property: p</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.p</code>&#x7684;<code>configurable</code>&#x4E3A;<code>false</code>&#x3002;&#x7136;&#x540E;&#xFF0C;&#x6539;&#x52A8;<code>value</code>&#x3001;<code>writable</code>&#x3001;<code>enumerable</code>&#x3001;<code>configurable</code>&#xFF0C;&#x7ED3;&#x679C;&#x90FD;&#x62A5;&#x9519;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;<code>writable</code>&#x53EA;&#x6709;&#x5728;<code>false</code>&#x6539;&#x4E3A;<code>true</code>&#x4F1A;&#x62A5;&#x9519;&#xFF0C;<code>true</code>&#x6539;&#x4E3A;<code>false</code>&#x662F;&#x5141;&#x8BB8;&#x7684;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  writable: <span class="hljs-literal">true</span>,
  configurable: <span class="hljs-literal">false</span>
});

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {writable: <span class="hljs-literal">false</span>})
<span class="hljs-comment">// &#x4FEE;&#x6539;&#x6210;&#x529F;</span>
</code></pre>
<p>&#x81F3;&#x4E8E;<code>value</code>&#xFF0C;&#x53EA;&#x8981;<code>writable</code>&#x548C;<code>configurable</code>&#x6709;&#x4E00;&#x4E2A;&#x4E3A;<code>true</code>&#xFF0C;&#x5C31;&#x5141;&#x8BB8;&#x6539;&#x52A8;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> o1 = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-number">1</span>,
  writable: <span class="hljs-literal">true</span>,
  configurable: <span class="hljs-literal">false</span>
});

<span class="hljs-built_in">Object</span>.defineProperty(o1, <span class="hljs-string">&apos;p&apos;</span>, {value: <span class="hljs-number">2</span>})
<span class="hljs-comment">// &#x4FEE;&#x6539;&#x6210;&#x529F;</span>

<span class="hljs-keyword">var</span> o2 = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-number">1</span>,
  writable: <span class="hljs-literal">false</span>,
  configurable: <span class="hljs-literal">true</span>
});

<span class="hljs-built_in">Object</span>.defineProperty(o2, <span class="hljs-string">&apos;p&apos;</span>, {value: <span class="hljs-number">2</span>})
<span class="hljs-comment">// &#x4FEE;&#x6539;&#x6210;&#x529F;</span>
</code></pre>
<p>&#x53E6;&#x5916;&#xFF0C;<code>writable</code>&#x4E3A;<code>false</code>&#x65F6;&#xFF0C;&#x76F4;&#x63A5;&#x76EE;&#x6807;&#x5C5E;&#x6027;&#x8D4B;&#x503C;&#xFF0C;&#x4E0D;&#x62A5;&#x9519;&#xFF0C;&#x4F46;&#x4E0D;&#x4F1A;&#x6210;&#x529F;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-number">1</span>,
  writable: <span class="hljs-literal">false</span>,
  configurable: <span class="hljs-literal">false</span>
});

obj.p = <span class="hljs-number">2</span>;
obj.p <span class="hljs-comment">// 1</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.p</code>&#x7684;<code>writable</code>&#x4E3A;<code>false</code>&#xFF0C;&#x5BF9;<code>obj.p</code>&#x76F4;&#x63A5;&#x8D4B;&#x503C;&#x4E0D;&#x4F1A;&#x751F;&#x6548;&#x3002;&#x5982;&#x679C;&#x662F;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#xFF0C;&#x8FD8;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<p>&#x53EF;&#x914D;&#x7F6E;&#x6027;&#x51B3;&#x5B9A;&#x4E86;&#x76EE;&#x6807;&#x5C5E;&#x6027;&#x662F;&#x5426;&#x53EF;&#x4EE5;&#x88AB;&#x5220;&#x9664;&#xFF08;delete&#xFF09;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperties({}, {
  p1: { value: <span class="hljs-number">1</span>, configurable: <span class="hljs-literal">true</span> },
  p2: { value: <span class="hljs-number">2</span>, configurable: <span class="hljs-literal">false</span> }
});

<span class="hljs-keyword">delete</span> obj.p1 <span class="hljs-comment">// true</span>
<span class="hljs-keyword">delete</span> obj.p2 <span class="hljs-comment">// false</span>

obj.p1 <span class="hljs-comment">// undefined</span>
obj.p2 <span class="hljs-comment">// 2</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.p1</code>&#x7684;<code>configurable</code>&#x662F;<code>true</code>&#xFF0C;&#x6240;&#x4EE5;&#x53EF;&#x4EE5;&#x88AB;&#x5220;&#x9664;&#xFF0C;<code>obj.p2</code>&#x5C31;&#x65E0;&#x6CD5;&#x5220;&#x9664;&#x3002;</p>
<h2 id="&#x5B58;&#x53D6;&#x5668;">&#x5B58;&#x53D6;&#x5668;</h2>
<p>&#x9664;&#x4E86;&#x76F4;&#x63A5;&#x5B9A;&#x4E49;&#x4EE5;&#x5916;&#xFF0C;&#x5C5E;&#x6027;&#x8FD8;&#x53EF;&#x4EE5;&#x7528;&#x5B58;&#x53D6;&#x5668;&#xFF08;accessor&#xFF09;&#x5B9A;&#x4E49;&#x3002;&#x5176;&#x4E2D;&#xFF0C;&#x5B58;&#x503C;&#x51FD;&#x6570;&#x79F0;&#x4E3A;<code>setter</code>&#xFF0C;&#x4F7F;&#x7528;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;<code>set</code>&#x5C5E;&#x6027;&#xFF1B;&#x53D6;&#x503C;&#x51FD;&#x6570;&#x79F0;&#x4E3A;<code>getter</code>&#xFF0C;&#x4F7F;&#x7528;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;<code>get</code>&#x5C5E;&#x6027;&#x3002;</p>
<p>&#x4E00;&#x65E6;&#x5BF9;&#x76EE;&#x6807;&#x5C5E;&#x6027;&#x5B9A;&#x4E49;&#x4E86;&#x5B58;&#x53D6;&#x5668;&#xFF0C;&#x90A3;&#x4E48;&#x5B58;&#x53D6;&#x7684;&#x65F6;&#x5019;&#xFF0C;&#x90FD;&#x5C06;&#x6267;&#x884C;&#x5BF9;&#x5E94;&#x7684;&#x51FD;&#x6570;&#x3002;&#x5229;&#x7528;&#x8FD9;&#x4E2A;&#x529F;&#x80FD;&#xFF0C;&#x53EF;&#x4EE5;&#x5B9E;&#x73B0;&#x8BB8;&#x591A;&#x9AD8;&#x7EA7;&#x7279;&#x6027;&#xFF0C;&#x6BD4;&#x5982;&#x67D0;&#x4E2A;&#x5C5E;&#x6027;&#x7981;&#x6B62;&#x8D4B;&#x503C;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-built_in">Object</span>.defineProperty({}, <span class="hljs-string">&apos;p&apos;</span>, {
  get: <span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params"></span>) </span>{
    <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;getter&apos;</span>;
  },
  set: <span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params">value</span>) </span>{
    <span class="hljs-built_in">console</span>.log(<span class="hljs-string">&apos;setter: &apos;</span> + value);
  }
});

obj.p <span class="hljs-comment">// &quot;getter&quot;</span>
obj.p = <span class="hljs-number">123</span> <span class="hljs-comment">// &quot;setter: 123&quot;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.p</code>&#x5B9A;&#x4E49;&#x4E86;<code>get</code>&#x548C;<code>set</code>&#x5C5E;&#x6027;&#x3002;<code>obj.p</code>&#x53D6;&#x503C;&#x65F6;&#xFF0C;&#x5C31;&#x4F1A;&#x8C03;&#x7528;<code>get</code>&#xFF1B;&#x8D4B;&#x503C;&#x65F6;&#xFF0C;&#x5C31;&#x4F1A;&#x8C03;&#x7528;<code>set</code>&#x3002;</p>
<p>JavaScript &#x8FD8;&#x63D0;&#x4F9B;&#x4E86;&#x5B58;&#x53D6;&#x5668;&#x7684;&#x53E6;&#x4E00;&#x79CD;&#x5199;&#x6CD5;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {
  get p() {
    <span class="hljs-keyword">return</span> <span class="hljs-string">&apos;getter&apos;</span>;
  },
  set p(value) {
    <span class="hljs-built_in">console</span>.log(<span class="hljs-string">&apos;setter: &apos;</span> + value);
  }
};
</code></pre>
<p>&#x4E0A;&#x9762;&#x7684;&#x5199;&#x6CD5;&#x4E0E;&#x5B9A;&#x4E49;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x662F;&#x7B49;&#x4EF7;&#x7684;&#xFF0C;&#x800C;&#x4E14;&#x4F7F;&#x7528;&#x66F4;&#x5E7F;&#x6CDB;&#x3002;</p>
<p>&#x6CE8;&#x610F;&#xFF0C;&#x53D6;&#x503C;&#x51FD;&#x6570;<code>get</code>&#x4E0D;&#x80FD;&#x63A5;&#x53D7;&#x53C2;&#x6570;&#xFF0C;&#x5B58;&#x503C;&#x51FD;&#x6570;<code>set</code>&#x53EA;&#x80FD;&#x63A5;&#x53D7;&#x4E00;&#x4E2A;&#x53C2;&#x6570;&#xFF08;&#x5373;&#x5C5E;&#x6027;&#x7684;&#x503C;&#xFF09;&#x3002;</p>
<p>&#x5B58;&#x53D6;&#x5668;&#x5F80;&#x5F80;&#x7528;&#x4E8E;&#xFF0C;&#x5C5E;&#x6027;&#x7684;&#x503C;&#x4F9D;&#x8D56;&#x5BF9;&#x8C61;&#x5185;&#x90E8;&#x6570;&#x636E;&#x7684;&#x573A;&#x5408;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj ={
  $n : <span class="hljs-number">5</span>,
  get next() { <span class="hljs-keyword">return</span> <span class="hljs-keyword">this</span>.$n++ },
  set next(n) {
    <span class="hljs-keyword">if</span> (n &gt;= <span class="hljs-keyword">this</span>.$n) <span class="hljs-keyword">this</span>.$n = n;
    <span class="hljs-keyword">else</span> <span class="hljs-keyword">throw</span> <span class="hljs-keyword">new</span> <span class="hljs-built_in">Error</span>(<span class="hljs-string">&apos;&#x65B0;&#x7684;&#x503C;&#x5FC5;&#x987B;&#x5927;&#x4E8E;&#x5F53;&#x524D;&#x503C;&apos;</span>);
  }
};

obj.next <span class="hljs-comment">// 5</span>

obj.next = <span class="hljs-number">10</span>;
obj.next <span class="hljs-comment">// 10</span>

obj.next = <span class="hljs-number">5</span>;
<span class="hljs-comment">// Uncaught Error: &#x65B0;&#x7684;&#x503C;&#x5FC5;&#x987B;&#x5927;&#x4E8E;&#x5F53;&#x524D;&#x503C;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>next</code>&#x5C5E;&#x6027;&#x7684;&#x5B58;&#x503C;&#x51FD;&#x6570;&#x548C;&#x53D6;&#x503C;&#x51FD;&#x6570;&#xFF0C;&#x90FD;&#x4F9D;&#x8D56;&#x4E8E;&#x5185;&#x90E8;&#x5C5E;&#x6027;<code>$n</code>&#x3002;</p>
<h2 id="&#x5BF9;&#x8C61;&#x7684;&#x62F7;&#x8D1D;">&#x5BF9;&#x8C61;&#x7684;&#x62F7;&#x8D1D;</h2>
<p>&#x6709;&#x65F6;&#xFF0C;&#x6211;&#x4EEC;&#x9700;&#x8981;&#x5C06;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x7684;&#x6240;&#x6709;&#x5C5E;&#x6027;&#xFF0C;&#x62F7;&#x8D1D;&#x5230;&#x53E6;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x53EF;&#x4EE5;&#x7528;&#x4E0B;&#x9762;&#x7684;&#x65B9;&#x6CD5;&#x5B9E;&#x73B0;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> extend = <span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params">to, from</span>) </span>{
  <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> property <span class="hljs-keyword">in</span> <span class="hljs-keyword">from</span>) {
    to[property] = <span class="hljs-keyword">from</span>[property];
  }

  <span class="hljs-keyword">return</span> to;
}

extend({}, {
  a: <span class="hljs-number">1</span>
})
<span class="hljs-comment">// {a: 1}</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x8FD9;&#x4E2A;&#x65B9;&#x6CD5;&#x7684;&#x95EE;&#x9898;&#x5728;&#x4E8E;&#xFF0C;&#x5982;&#x679C;&#x9047;&#x5230;&#x5B58;&#x53D6;&#x5668;&#x5B9A;&#x4E49;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x4F1A;&#x53EA;&#x62F7;&#x8D1D;&#x503C;&#x3002;</p>
<pre><code class="lang-javascript">extend({}, {
  get a() { <span class="hljs-keyword">return</span> <span class="hljs-number">1</span> }
})
<span class="hljs-comment">// {a: 1}</span>
</code></pre>
<p>&#x4E3A;&#x4E86;&#x89E3;&#x51B3;&#x8FD9;&#x4E2A;&#x95EE;&#x9898;&#xFF0C;&#x6211;&#x4EEC;&#x53EF;&#x4EE5;&#x901A;&#x8FC7;<code>Object.defineProperty</code>&#x65B9;&#x6CD5;&#x6765;&#x62F7;&#x8D1D;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> extend = <span class="hljs-function"><span class="hljs-keyword">function</span> (<span class="hljs-params">to, from</span>) </span>{
  <span class="hljs-keyword">for</span> (<span class="hljs-keyword">var</span> property <span class="hljs-keyword">in</span> <span class="hljs-keyword">from</span>) {
    <span class="hljs-keyword">if</span> (!<span class="hljs-keyword">from</span>.hasOwnProperty(property)) <span class="hljs-keyword">continue</span>;
    <span class="hljs-built_in">Object</span>.defineProperty(
      to,
      property,
      <span class="hljs-built_in">Object</span>.getOwnPropertyDescriptor(<span class="hljs-keyword">from</span>, property)
    );
  }

  <span class="hljs-keyword">return</span> to;
}

extend({}, { get a(){ <span class="hljs-keyword">return</span> <span class="hljs-number">1</span> } })
<span class="hljs-comment">// { get a(){ return 1 } })</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>hasOwnProperty</code>&#x90A3;&#x4E00;&#x884C;&#x7528;&#x6765;&#x8FC7;&#x6EE4;&#x6389;&#x7EE7;&#x627F;&#x7684;&#x5C5E;&#x6027;&#xFF0C;&#x5426;&#x5219;&#x53EF;&#x80FD;&#x4F1A;&#x62A5;&#x9519;&#xFF0C;&#x56E0;&#x4E3A;<code>Object.getOwnPropertyDescriptor</code>&#x8BFB;&#x4E0D;&#x5230;&#x7EE7;&#x627F;&#x5C5E;&#x6027;&#x7684;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x3002;</p>
<h2 id="&#x63A7;&#x5236;&#x5BF9;&#x8C61;&#x72B6;&#x6001;">&#x63A7;&#x5236;&#x5BF9;&#x8C61;&#x72B6;&#x6001;</h2>
<p>&#x6709;&#x65F6;&#x9700;&#x8981;&#x51BB;&#x7ED3;&#x5BF9;&#x8C61;&#x7684;&#x8BFB;&#x5199;&#x72B6;&#x6001;&#xFF0C;&#x9632;&#x6B62;&#x5BF9;&#x8C61;&#x88AB;&#x6539;&#x53D8;&#x3002;JavaScript &#x63D0;&#x4F9B;&#x4E86;&#x4E09;&#x79CD;&#x51BB;&#x7ED3;&#x65B9;&#x6CD5;&#xFF0C;&#x6700;&#x5F31;&#x7684;&#x4E00;&#x79CD;&#x662F;<code>Object.preventExtensions</code>&#xFF0C;&#x5176;&#x6B21;&#x662F;<code>Object.seal</code>&#xFF0C;&#x6700;&#x5F3A;&#x7684;&#x662F;<code>Object.freeze</code>&#x3002;</p>
<h3 id="objectpreventextensions">Object.preventExtensions()</h3>
<p><code>Object.preventExtensions</code>&#x65B9;&#x6CD5;&#x53EF;&#x4EE5;&#x4F7F;&#x5F97;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x65E0;&#x6CD5;&#x518D;&#x6DFB;&#x52A0;&#x65B0;&#x7684;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Object</span>();
<span class="hljs-built_in">Object</span>.preventExtensions(obj);

<span class="hljs-built_in">Object</span>.defineProperty(obj, <span class="hljs-string">&apos;p&apos;</span>, {
  value: <span class="hljs-string">&apos;hello&apos;</span>
});
<span class="hljs-comment">// TypeError: Cannot define property:p, object is not extensible.</span>

obj.p = <span class="hljs-number">1</span>;
obj.p <span class="hljs-comment">// undefined</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj</code>&#x5BF9;&#x8C61;&#x7ECF;&#x8FC7;<code>Object.preventExtensions</code>&#x4EE5;&#x540E;&#xFF0C;&#x5C31;&#x65E0;&#x6CD5;&#x6DFB;&#x52A0;&#x65B0;&#x5C5E;&#x6027;&#x4E86;&#x3002;</p>
<h3 id="objectisextensible">Object.isExtensible()</h3>
<p><code>Object.isExtensible</code>&#x65B9;&#x6CD5;&#x7528;&#x4E8E;&#x68C0;&#x67E5;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x662F;&#x5426;&#x4F7F;&#x7528;&#x4E86;<code>Object.preventExtensions</code>&#x65B9;&#x6CD5;&#x3002;&#x4E5F;&#x5C31;&#x662F;&#x8BF4;&#xFF0C;&#x68C0;&#x67E5;&#x662F;&#x5426;&#x53EF;&#x4EE5;&#x4E3A;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x6DFB;&#x52A0;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Object</span>();

<span class="hljs-built_in">Object</span>.isExtensible(obj) <span class="hljs-comment">// true</span>
<span class="hljs-built_in">Object</span>.preventExtensions(obj);
<span class="hljs-built_in">Object</span>.isExtensible(obj) <span class="hljs-comment">// false</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x5BF9;<code>obj</code>&#x5BF9;&#x8C61;&#x4F7F;&#x7528;<code>Object.preventExtensions</code>&#x65B9;&#x6CD5;&#x4EE5;&#x540E;&#xFF0C;&#x518D;&#x4F7F;&#x7528;<code>Object.isExtensible</code>&#x65B9;&#x6CD5;&#xFF0C;&#x8FD4;&#x56DE;<code>false</code>&#xFF0C;&#x8868;&#x793A;&#x5DF2;&#x7ECF;&#x4E0D;&#x80FD;&#x6DFB;&#x52A0;&#x65B0;&#x5C5E;&#x6027;&#x4E86;&#x3002;</p>
<h3 id="objectseal">Object.seal()</h3>
<p><code>Object.seal</code>&#x65B9;&#x6CD5;&#x4F7F;&#x5F97;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x65E2;&#x65E0;&#x6CD5;&#x6DFB;&#x52A0;&#x65B0;&#x5C5E;&#x6027;&#xFF0C;&#x4E5F;&#x65E0;&#x6CD5;&#x5220;&#x9664;&#x65E7;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = { p: <span class="hljs-string">&apos;hello&apos;</span> };
<span class="hljs-built_in">Object</span>.seal(obj);

<span class="hljs-keyword">delete</span> obj.p;
obj.p <span class="hljs-comment">// &quot;hello&quot;</span>

obj.x = <span class="hljs-string">&apos;world&apos;</span>;
obj.x <span class="hljs-comment">// undefined</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj</code>&#x5BF9;&#x8C61;&#x6267;&#x884C;<code>Object.seal</code>&#x65B9;&#x6CD5;&#x4EE5;&#x540E;&#xFF0C;&#x5C31;&#x65E0;&#x6CD5;&#x6DFB;&#x52A0;&#x65B0;&#x5C5E;&#x6027;&#x548C;&#x5220;&#x9664;&#x65E7;&#x5C5E;&#x6027;&#x4E86;&#x3002;</p>
<p><code>Object.seal</code>&#x5B9E;&#x8D28;&#x662F;&#x628A;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;<code>configurable</code>&#x5C5E;&#x6027;&#x8BBE;&#x4E3A;<code>false</code>&#xFF0C;&#x56E0;&#x6B64;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x4E0D;&#x518D;&#x80FD;&#x6539;&#x53D8;&#x4E86;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {
  p: <span class="hljs-string">&apos;a&apos;</span>
};

<span class="hljs-comment">// seal&#x65B9;&#x6CD5;&#x4E4B;&#x524D;</span>
<span class="hljs-built_in">Object</span>.getOwnPropertyDescriptor(obj, <span class="hljs-string">&apos;p&apos;</span>)
<span class="hljs-comment">// Object {</span>
<span class="hljs-comment">//   value: &quot;a&quot;,</span>
<span class="hljs-comment">//   writable: true,</span>
<span class="hljs-comment">//   enumerable: true,</span>
<span class="hljs-comment">//   configurable: true</span>
<span class="hljs-comment">// }</span>

<span class="hljs-built_in">Object</span>.seal(obj);

<span class="hljs-comment">// seal&#x65B9;&#x6CD5;&#x4E4B;&#x540E;</span>
<span class="hljs-built_in">Object</span>.getOwnPropertyDescriptor(obj, <span class="hljs-string">&apos;p&apos;</span>)
<span class="hljs-comment">// Object {</span>
<span class="hljs-comment">//   value: &quot;a&quot;,</span>
<span class="hljs-comment">//   writable: true,</span>
<span class="hljs-comment">//   enumerable: true,</span>
<span class="hljs-comment">//   configurable: false</span>
<span class="hljs-comment">// }</span>

<span class="hljs-built_in">Object</span>.defineProperty(o, <span class="hljs-string">&apos;p&apos;</span>, {
  enumerable: <span class="hljs-literal">false</span>
})
<span class="hljs-comment">// TypeError: Cannot redefine property: p</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x4F7F;&#x7528;<code>Object.seal</code>&#x65B9;&#x6CD5;&#x4E4B;&#x540E;&#xFF0C;&#x5C5E;&#x6027;&#x63CF;&#x8FF0;&#x5BF9;&#x8C61;&#x7684;<code>configurable</code>&#x5C5E;&#x6027;&#x5C31;&#x53D8;&#x6210;&#x4E86;<code>false</code>&#xFF0C;&#x7136;&#x540E;&#x6539;&#x53D8;<code>enumerable</code>&#x5C5E;&#x6027;&#x5C31;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<p><code>Object.seal</code>&#x53EA;&#x662F;&#x7981;&#x6B62;&#x65B0;&#x589E;&#x6216;&#x5220;&#x9664;&#x5C5E;&#x6027;&#xFF0C;&#x5E76;&#x4E0D;&#x5F71;&#x54CD;&#x4FEE;&#x6539;&#x67D0;&#x4E2A;&#x5C5E;&#x6027;&#x7684;&#x503C;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = { p: <span class="hljs-string">&apos;a&apos;</span> };
<span class="hljs-built_in">Object</span>.seal(obj);
obj.p = <span class="hljs-string">&apos;b&apos;</span>;
obj.p <span class="hljs-comment">// &apos;b&apos;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>Object.seal</code>&#x65B9;&#x6CD5;&#x5BF9;<code>p</code>&#x5C5E;&#x6027;&#x7684;<code>value</code>&#x65E0;&#x6548;&#xFF0C;&#x662F;&#x56E0;&#x4E3A;&#x6B64;&#x65F6;<code>p</code>&#x5C5E;&#x6027;&#x7684;&#x53EF;&#x5199;&#x6027;&#x7531;<code>writable</code>&#x51B3;&#x5B9A;&#x3002;</p>
<h3 id="objectissealed">Object.isSealed()</h3>
<p><code>Object.isSealed</code>&#x65B9;&#x6CD5;&#x7528;&#x4E8E;&#x68C0;&#x67E5;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x662F;&#x5426;&#x4F7F;&#x7528;&#x4E86;<code>Object.seal</code>&#x65B9;&#x6CD5;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = { p: <span class="hljs-string">&apos;a&apos;</span> };

<span class="hljs-built_in">Object</span>.seal(obj);
<span class="hljs-built_in">Object</span>.isSealed(obj) <span class="hljs-comment">// true</span>
</code></pre>
<p>&#x8FD9;&#x65F6;&#xFF0C;<code>Object.isExtensible</code>&#x65B9;&#x6CD5;&#x4E5F;&#x8FD4;&#x56DE;<code>false</code>&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = { p: <span class="hljs-string">&apos;a&apos;</span> };

<span class="hljs-built_in">Object</span>.seal(obj);
<span class="hljs-built_in">Object</span>.isExtensible(obj) <span class="hljs-comment">// false</span>
</code></pre>
<h3 id="objectfreeze">Object.freeze()</h3>
<p><code>Object.freeze</code>&#x65B9;&#x6CD5;&#x53EF;&#x4EE5;&#x4F7F;&#x5F97;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x65E0;&#x6CD5;&#x6DFB;&#x52A0;&#x65B0;&#x5C5E;&#x6027;&#x3001;&#x65E0;&#x6CD5;&#x5220;&#x9664;&#x65E7;&#x5C5E;&#x6027;&#x3001;&#x4E5F;&#x65E0;&#x6CD5;&#x6539;&#x53D8;&#x5C5E;&#x6027;&#x7684;&#x503C;&#xFF0C;&#x4F7F;&#x5F97;&#x8FD9;&#x4E2A;&#x5BF9;&#x8C61;&#x5B9E;&#x9645;&#x4E0A;&#x53D8;&#x6210;&#x4E86;&#x5E38;&#x91CF;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {
  p: <span class="hljs-string">&apos;hello&apos;</span>
};

<span class="hljs-built_in">Object</span>.freeze(obj);

obj.p = <span class="hljs-string">&apos;world&apos;</span>;
obj.p <span class="hljs-comment">// &quot;hello&quot;</span>

obj.t = <span class="hljs-string">&apos;hello&apos;</span>;
obj.t <span class="hljs-comment">// undefined</span>

<span class="hljs-keyword">delete</span> obj.p <span class="hljs-comment">// false</span>
obj.p <span class="hljs-comment">// &quot;hello&quot;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x5BF9;<code>obj</code>&#x5BF9;&#x8C61;&#x8FDB;&#x884C;<code>Object.freeze()</code>&#x4EE5;&#x540E;&#xFF0C;&#x4FEE;&#x6539;&#x5C5E;&#x6027;&#x3001;&#x65B0;&#x589E;&#x5C5E;&#x6027;&#x3001;&#x5220;&#x9664;&#x5C5E;&#x6027;&#x90FD;&#x65E0;&#x6548;&#x4E86;&#x3002;&#x8FD9;&#x4E9B;&#x64CD;&#x4F5C;&#x5E76;&#x4E0D;&#x62A5;&#x9519;&#xFF0C;&#x53EA;&#x662F;&#x9ED8;&#x9ED8;&#x5730;&#x5931;&#x8D25;&#x3002;&#x5982;&#x679C;&#x5728;&#x4E25;&#x683C;&#x6A21;&#x5F0F;&#x4E0B;&#xFF0C;&#x5219;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<h3 id="objectisfrozen">Object.isFrozen()</h3>
<p><code>Object.isFrozen</code>&#x65B9;&#x6CD5;&#x7528;&#x4E8E;&#x68C0;&#x67E5;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#x662F;&#x5426;&#x4F7F;&#x7528;&#x4E86;<code>Object.freeze</code>&#x65B9;&#x6CD5;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {
  p: <span class="hljs-string">&apos;hello&apos;</span>
};

<span class="hljs-built_in">Object</span>.freeze(obj);
<span class="hljs-built_in">Object</span>.isFrozen(obj) <span class="hljs-comment">// true</span>
</code></pre>
<p>&#x4F7F;&#x7528;<code>Object.freeze</code>&#x65B9;&#x6CD5;&#x4EE5;&#x540E;&#xFF0C;<code>Object.isSealed</code>&#x5C06;&#x4F1A;&#x8FD4;&#x56DE;<code>true</code>&#xFF0C;<code>Object.isExtensible</code>&#x8FD4;&#x56DE;<code>false</code>&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {
  p: <span class="hljs-string">&apos;hello&apos;</span>
};

<span class="hljs-built_in">Object</span>.freeze(obj);

<span class="hljs-built_in">Object</span>.isSealed(obj) <span class="hljs-comment">// true</span>
<span class="hljs-built_in">Object</span>.isExtensible(obj) <span class="hljs-comment">// false</span>
</code></pre>
<p><code>Object.isFrozen</code>&#x7684;&#x4E00;&#x4E2A;&#x7528;&#x9014;&#x662F;&#xFF0C;&#x786E;&#x8BA4;&#x67D0;&#x4E2A;&#x5BF9;&#x8C61;&#x6CA1;&#x6709;&#x88AB;&#x51BB;&#x7ED3;&#x540E;&#xFF0C;&#x518D;&#x5BF9;&#x5B83;&#x7684;&#x5C5E;&#x6027;&#x8D4B;&#x503C;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {
  p: <span class="hljs-string">&apos;hello&apos;</span>
};

<span class="hljs-built_in">Object</span>.freeze(obj);

<span class="hljs-keyword">if</span> (!<span class="hljs-built_in">Object</span>.isFrozen(obj)) {
  obj.p = <span class="hljs-string">&apos;world&apos;</span>;
}
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x786E;&#x8BA4;<code>obj</code>&#x6CA1;&#x6709;&#x88AB;&#x51BB;&#x7ED3;&#x540E;&#xFF0C;&#x518D;&#x5BF9;&#x5B83;&#x7684;&#x5C5E;&#x6027;&#x8D4B;&#x503C;&#xFF0C;&#x5C31;&#x4E0D;&#x4F1A;&#x62A5;&#x9519;&#x4E86;&#x3002;</p>
<h3 id="&#x5C40;&#x9650;&#x6027;">&#x5C40;&#x9650;&#x6027;</h3>
<p>&#x4E0A;&#x9762;&#x7684;&#x4E09;&#x4E2A;&#x65B9;&#x6CD5;&#x9501;&#x5B9A;&#x5BF9;&#x8C61;&#x7684;&#x53EF;&#x5199;&#x6027;&#x6709;&#x4E00;&#x4E2A;&#x6F0F;&#x6D1E;&#xFF1A;&#x53EF;&#x4EE5;&#x901A;&#x8FC7;&#x6539;&#x53D8;&#x539F;&#x578B;&#x5BF9;&#x8C61;&#xFF0C;&#x6765;&#x4E3A;&#x5BF9;&#x8C61;&#x589E;&#x52A0;&#x5C5E;&#x6027;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Object</span>();
<span class="hljs-built_in">Object</span>.preventExtensions(obj);

<span class="hljs-keyword">var</span> proto = <span class="hljs-built_in">Object</span>.getPrototypeOf(obj);
proto.t = <span class="hljs-string">&apos;hello&apos;</span>;
obj.t
<span class="hljs-comment">// hello</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;&#x5BF9;&#x8C61;<code>obj</code>&#x672C;&#x8EAB;&#x4E0D;&#x80FD;&#x65B0;&#x589E;&#x5C5E;&#x6027;&#xFF0C;&#x4F46;&#x662F;&#x53EF;&#x4EE5;&#x5728;&#x5B83;&#x7684;&#x539F;&#x578B;&#x5BF9;&#x8C61;&#x4E0A;&#x65B0;&#x589E;&#x5C5E;&#x6027;&#xFF0C;&#x5C31;&#x4F9D;&#x7136;&#x80FD;&#x591F;&#x5728;<code>obj</code>&#x4E0A;&#x8BFB;&#x5230;&#x3002;</p>
<p>&#x4E00;&#x79CD;&#x89E3;&#x51B3;&#x65B9;&#x6848;&#x662F;&#xFF0C;&#x628A;<code>obj</code>&#x7684;&#x539F;&#x578B;&#x4E5F;&#x51BB;&#x7ED3;&#x4F4F;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = <span class="hljs-keyword">new</span> <span class="hljs-built_in">Object</span>();
<span class="hljs-built_in">Object</span>.preventExtensions(obj);

<span class="hljs-keyword">var</span> proto = <span class="hljs-built_in">Object</span>.getPrototypeOf(obj);
<span class="hljs-built_in">Object</span>.preventExtensions(proto);

proto.t = <span class="hljs-string">&apos;hello&apos;</span>;
obj.t <span class="hljs-comment">// undefined</span>
</code></pre>
<p>&#x53E6;&#x5916;&#x4E00;&#x4E2A;&#x5C40;&#x9650;&#x662F;&#xFF0C;&#x5982;&#x679C;&#x5C5E;&#x6027;&#x503C;&#x662F;&#x5BF9;&#x8C61;&#xFF0C;&#x4E0A;&#x9762;&#x8FD9;&#x4E9B;&#x65B9;&#x6CD5;&#x53EA;&#x80FD;&#x51BB;&#x7ED3;&#x5C5E;&#x6027;&#x6307;&#x5411;&#x7684;&#x5BF9;&#x8C61;&#xFF0C;&#x800C;&#x4E0D;&#x80FD;&#x51BB;&#x7ED3;&#x5BF9;&#x8C61;&#x672C;&#x8EAB;&#x7684;&#x5185;&#x5BB9;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> obj = {
  foo: <span class="hljs-number">1</span>,
  bar: [<span class="hljs-string">&apos;a&apos;</span>, <span class="hljs-string">&apos;b&apos;</span>]
};
<span class="hljs-built_in">Object</span>.freeze(obj);

obj.bar.push(<span class="hljs-string">&apos;c&apos;</span>);
obj.bar <span class="hljs-comment">// [&quot;a&quot;, &quot;b&quot;, &quot;c&quot;]</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>obj.bar</code>&#x5C5E;&#x6027;&#x6307;&#x5411;&#x4E00;&#x4E2A;&#x6570;&#x7EC4;&#xFF0C;<code>obj</code>&#x5BF9;&#x8C61;&#x88AB;&#x51BB;&#x7ED3;&#x4EE5;&#x540E;&#xFF0C;&#x8FD9;&#x4E2A;&#x6307;&#x5411;&#x65E0;&#x6CD5;&#x6539;&#x53D8;&#xFF0C;&#x5373;&#x65E0;&#x6CD5;&#x6307;&#x5411;&#x5176;&#x4ED6;&#x503C;&#xFF0C;&#x4F46;&#x662F;&#x6240;&#x6307;&#x5411;&#x7684;&#x6570;&#x7EC4;&#x662F;&#x53EF;&#x4EE5;&#x6539;&#x53D8;&#x7684;&#x3002;</p>




<footer class="page-footer-ex"> <span class="page-footer-ex-copyright"> <a href="https://xiaobaiai.net" target="_blank" rel="nofollow">&#x5C0F;&#x767D;AI.&#x6613;&#x540D;</a>, &#x4F7F;&#x7528;<a href="https://creativecommons.org/licenses/by-sa/4.0/" target="_blank" rel="nofollow">&#x77E5;&#x8BC6;&#x5171;&#x4EAB; 4.0 &#x534F;&#x8BAE;&#x53D1;&#x5E03;</a>&#x53D1;&#x5E03; </span> &#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0;&#xA0; <span class="page-footer-ex-footer-update"> <i>&#x9875;&#x9762;&#x4FEE;&#x8BA2;&#x4E8E;&#xFF1A;</i> 2019-08-22 16:53:02 </span> </footer>
                                
                                </section>
                            
    </div>
    <div class="search-results">
        <div class="has-results">
            
            <h1 class="search-results-title"><span class='search-results-count'></span> results matching "<span class='search-query'></span>"</h1>
            <ul class="search-results-list"></ul>
            
        </div>
        <div class="no-results">
            
            <h1 class="search-results-title">No results matching "<span class='search-query'></span>"</h1>
            
        </div>
    </div>
</div>

    </div>
    <div class="search-results">
        <div class="has-results">
            
            <h1 class="search-results-title"><span class='search-results-count'></span> results matching "<span class='search-query'></span>"</h1>
            <ul class="search-results-list"></ul>
            
        </div>
        <div class="no-results">
            
            <h1 class="search-results-title">No results matching "<span class='search-query'></span>"</h1>
            
        </div>
    </div>
</div>

                        </div>
                    </div>
                
            </div>

            
                
                <a href="object.html" class="navigation navigation-prev " aria-label="Previous page: Object 对象">
                    <i class="fa fa-angle-left"></i>
                </a>
                
                
                <a href="array.html" class="navigation navigation-next " aria-label="Next page: Array 对象">
                    <i class="fa fa-angle-right"></i>
                </a>
                
            
        
    </div>

    <script>
        var gitbook = gitbook || [];
        gitbook.push(function() {
            gitbook.page.hasChanged({"page":{"title":"属性描述对象","level":"1.6.2","depth":2,"next":{"title":"Array 对象","level":"1.6.3","depth":2,"path":"docs/stdlib/array.md","ref":"docs/stdlib/array.md","articles":[]},"previous":{"title":"Object 对象","level":"1.6.1","depth":2,"path":"docs/stdlib/object.md","ref":"docs/stdlib/object.md","articles":[]},"dir":"ltr"},"config":{"plugins":["-sharing","chapter-fold","back-to-top-button","search-pro","sharing-plus","myseo","favicon","page-footer-ex","search-pro","livereload"],"styles":{"website":"styles/website.css","pdf":"styles/pdf.css","epub":"styles/epub.css","mobi":"styles/mobi.css","ebook":"styles/ebook.css","print":"styles/print.css"},"pluginsConfig":{"chapter-fold":{},"livereload":{},"page-footer-ex":{"copyright":"<a href='https://xiaobaiai.net' target='_blank'>小白AI.易名</a>, 使用<a href='https://creativecommons.org/licenses/by-sa/4.0/' target='_blank'>知识共享 4.0 协议发布</a>发布","markdown":false,"update_format":"YYYY-MM-DD HH:mm:ss","update_label":"<i>页面修订于：</i>"},"search-pro":{},"search":{},"sharing-plus":{"qq":false,"all":["facebook","google","twitter","instapaper","linkedin","pocket","stumbleupon"],"douban":false,"facebook":true,"weibo":false,"instapaper":false,"whatsapp":false,"hatenaBookmark":false,"twitter":true,"messenger":false,"line":false,"vk":false,"pocket":true,"google":false,"viber":false,"stumbleupon":false,"qzone":false,"linkedin":false},"lunr":{"maxIndexSize":1000000,"ignoreSpecialCharacters":false},"myseo":{"description":"Javascript教程","keywords":"小白AI.易名,xiaobaiai.net,Javascript,入门,教程,博客","titlePrefix":"Javascript教程 - ","titleSuffix":" - 小白AI.易名"},"fontsettings":{"theme":"white","family":"sans","size":2},"highlight":{},"favicon":{"shortcut":"assets/images/favicon.ico","bookmark":"assets/images/favicon.ico","appleTouch":"assets/images/apple-touch-icon.png","appleTouchMore":{"120x120":"assets/images/apple-touch-icon-120x120.png","180x180":"assets/images/apple-touch-icon-180x180.png"}},"back-to-top-button":{},"sharing":{"qq":true,"all":["qq","qzone","twitter","weibo","linkedin"],"douban":false,"facebook":true,"weibo":true,"instapaper":false,"whatsapp":false,"hatenaBookmark":false,"twitter":false,"messenger":false,"line":false,"vk":false,"pocket":false,"google":false,"viber":false,"stumbleupon":false,"qzone":true,"linkedin":false},"theme-default":{"styles":{"website":"styles/website.css","pdf":"styles/pdf.css","epub":"styles/epub.css","mobi":"styles/mobi.css","ebook":"styles/ebook.css","print":"styles/print.css"},"showLevel":false}},"theme":"default","author":"小白AI.易名","pdf":{"pageNumbers":true,"fontSize":12,"fontFamily":"Arial","paperSize":"a4","chapterMark":"pagebreak","pageBreaksBefore":"/","margin":{"right":62,"left":62,"top":56,"bottom":56}},"structure":{"langs":"LANGS.md","readme":"README.md","glossary":"GLOSSARY.md","summary":"SUMMARY.md"},"variables":{},"language":"zh-hans","gitbook":"*","description":"Javascript教程"},"file":{"path":"docs/stdlib/attributes.md","mtime":"2019-08-22T08:53:02.371Z","type":"markdown"},"gitbook":{"version":"3.2.3","time":"2019-08-28T05:00:46.673Z"},"basePath":"../..","book":{"language":""}});
        });
    </script>
</div>

        
    <script src="../../gitbook/gitbook.js"></script>
    <script src="../../gitbook/theme.js"></script>
    
        
        <script src="../../gitbook/gitbook-plugin-chapter-fold/chapter-fold.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-back-to-top-button/plugin.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-search-pro/jquery.mark.min.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-search-pro/search.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-sharing-plus/buttons.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-livereload/plugin.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-search/search-engine.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-search/search.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-lunr/lunr.min.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-lunr/search-lunr.js"></script>
        
    
        
        <script src="../../gitbook/gitbook-plugin-fontsettings/fontsettings.js"></script>
        
    

    </body>
</html>

